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EXPERIMENTS ON AUTOMATIC DIGITIZING OF CARTOGRAPHIC MAPS 
BY MEANS OF COLOUR-SCANNERS 
W. Lichtner 
Technical University of Darmstadt, FRG 
ABSTRACT 
For computer-aided cartographic processes and for the gene 
ration of a cartographic data base it's often necessary to 
digitize a lot of map gheets. Conventionally it's done by 
following the lines on a table-digitizer manually. This 
process is error-prone and very time-consuming. One possible 
way to replace manual digitization by an automatic method 
- in addition to an automatic 1ine-fo11owing-system - is 
scanning a printing original of a map and extracting the 
line work from the resulting binary matrix. 
For some time past do exist an usable software development 
of the "Gesellschaft fur Mathematik und Datenverarbeitung - 
Bonn (GMD)" (Woetzel 1977) for topological skeletonizing 
and line- and node-extraction from binary matrices. Tests 
with printing originals containing only one feature quality 
(e.g. contour-lines or border lines of the same quality) 
have been carried out successfully. But an important 
restriction is the fact that different qualities of carto 
graphic features could not classified automatically. That's 
the reason why we confine the usage of this program to 
graphic representations containing only one feature quality 
(e.g. contour-lines only). This restriction is very 
disagreeable to automatic digitizing of cartographic maps. 
In conventional cartography we have several separated 
printing originals in order to offer a certain possibility 
of combinations. These foils once being produced (e.g. 
planimetry foil of a topographic map) contain cartographic 
features of different qualities generally (conventional 
signs of streets, houses, rivers and other topographic 
features). Today we have no usable software for the auto 
matic extraction and classification of such cartographic 
printing originals. 
The author describes his own experiments to bridge over 
this problem by means of a simple manual preliminary working 
process and by using a colour-scanner. It was the target of 
the experiments to scan a prepared planimetry foil of a topo 
graphic basic map at the scale 1:5,000 with the aid of a 
colour-scanner and to create by means of digital image 
procedures feature-qua1ity-se1ected image matrices which can 
be subsequent processed individually by the above noted 
program for the topological skeletonizing and line- and 
node-extraction.